Is it possible to make a Raid 5 sata that will act a a file server on a network, and have everything you need to manage it run from a bootable Linux Live CD ( Possibly Knoppix ) ?

I am thinking along these lines since a lot of the affordable NAS devices don't allow you to tinker with the embeded OS that comes with the unit.
For exemple, if I wanted pre built NAS to use a firewall and one didn't come with it, I'm stuck. If it was run from a Live CD, you would never have to worry about it getting hacked since the OS is run from the CD.